Solar cell arrays are provided on satellites to charge batteries which, in turn, provide power to the electrical components of the satellite. Power regulators are required for optimum battery charging and maintenance. For example, some satellites have orbits in which the satellite is out of view of the sun periodically. When the sun comes back in view, the cold solar cell arrays are highly efficient and provide very high power output. Without power regulators, the high power output of a solar cell array could overdrive the batteries or create excessive voltages.
Various methods are used to provide regulation for solar cell array generated power. Current techniques, such as cell string switching and switching regulatory architectures, require switching of transistors at high speeds, typically between 100-1000 times per second. The noise and accompanying transients produced by the switching transistors must be filtered to meet EMI requirements. In order to meet these requirements, extra circuitry and structural components are necessary, thereby adding weight to the satellite. Generally, these regulators require a lot of heavy wiring (typically copper) to implement the voltage regulation. Also, weight is added from other structural components that are necessary for protecting standard electronic hardware from the environments of orbit, such as large temperature changes (+125.degree. C. to -140.degree. C.), numerous temperature cycles (3,000 to 30,000 earth orbits), and high radiation (4 megarad). The waste heat of a switching regulator is normally conducted away by a thermal control pallet, which typically weighs 10 pounds for every 1000 watts handled by the regulator.
The previous systems perform a discrete shunt, thereby causing the solar array to remain hot during an off shunt. Heat build-up degrades the solar array performance and efficiency over time. Also, these systems are custom designed to support the solar array they are to function with. If the power requirements and the solar array are changed, the regulator must be redesigned, with an obvious increase in cost.